For centuries individuals, governments, and business entities have searched for mechanisms and techniques whereby sensitive information may be transmitted to authorized parties over long distances and still remain secure. The problem faced by the foregoing entities is how can information be sent to the individual or entities that require it and still be assured that unauthorized parties may not be able to comprehend the transmitted information should they intercept it. Early methods of securing information have employed scrambling techniques, lookup tables, substitution ciphers, and code books in which letters or terms would be substituted for the original letters and terms in the information. These techniques frequently required that both the sender and receiver of information have access to the same code book. One danger in such a technique is that the code book would fall into unauthorized hands.
In the early twentieth century, and particularly during World War II code books were replaced by electromechanical cipher machines. Both the sender and receiver would have an identical cipher machine used to encrypt and decrypt messages sent. In order to make it more difficult to decrypt these messages the cipher machines have the ability to change the cipher used in a message or change the cipher used for every few words within a message. In order to accomplish this the cipher machine would need to know the initial state or key utilized to encrypt the message.
In recent years the cipher machines have been replaced by digital encryption algorithms in which both the sender and receiver have an identical copy of the digital encryption algorithm and a common key used to encrypt and decrypt messages. Both the encryption algorithm and key are held secret by both the sender and receiver.
More recently another encryption technique has been developed in which two separate keys are used for encryption and decryption. A public key is transmitted freely to whoever requires it and is used to encrypt messages for a particular receiver. The receiver would have an associated private key which may be used to decrypt the message encrypted with the associated public key. For each public key there is only one private key and for each private key there is only one public key. When sending a message to several recipients it is necessary to have each recipient's public key. The message would then be separately encrypted using each recipient's public key and transmitted to that particular recipient. Therefore, if ten separate entities are to receive the same message, ten separate messages would be transmitted with each message encrypted with individual's public key. With the advent of the Internet, such a public key infrastructure has gained significant acceptance as discussed in request for comments number 2459, by Ford et al., entitled “Internet X.509 Public Key Infrastructure”, herein incorporated in its entirety by reference.
In addition to the need for the encryption and decryption of messages, with the advent of electronic mail and the Internet a need has developed for a secure mechanism to indicate approval and acceptance by an individual. In the past an individual would typically show his approval or acceptance of such items as a contract or an order via a handwritten signature, a stamp, or a seal which would only be held by that individual. Anyone else that attempted to imitate such a signature, stamp, or seal would be subject to criminal penalties. With the advent of electronic mail and the Internet, a need has arisen to take advantage of the ease and speed of electronic mail to indicate, by a person or entity with proper authority, approval or acceptance of a contract or purchase. This has come to be known as a digital signature in which an individual may digitally sign a document.
This digital signature capability has been implemented using the same public key infrastructure previously discussed. However, instead of an entire document being encrypted, the document itself is passed through a one-way hashing algorithm that produces a small document, referred to as a digest. This digest is then encrypted using the individual's private key, also known as a private signing key, and is appended to the document. The receiver of the document can verify the authenticity of the digital signature (digest) by stripping the signature from the document and recomputing the hash function on the document to generate as a received digest. Using public signing key, included in the document or previously received, it is possible to decrypt the digest of the document and compare it to the digest as received. If the two digest match, then the signature is authenticated. Therefore, using the aforementioned public key infrastructure it is possible to both encrypt and decrypt messages as well as digitally sign documents.
However, in the aforementioned public key infrastructure, in spite of the Internet X.509 infrastructure acceptance, certificates generated by one supplier's software may not be compatible with that of another supplier's software. For example, Microsoft™ in Windows 2000™ provides for the generation of digital certificates for the purpose of “single sign-on” by a user to a Microsoft™ network. Typically the user would request such a single sign-on certificate by utilizing a conventional web browser to access a domain certificate authority. The user would then fill in the requested information and the domain certificate authority may optionally require the concurrence of an administrator to approve the issuance of the certificate. It should be noted that the user is not required to provide any proof of identity and normally no authentication of identity occurs. However, the certificate issued is often only accepted by only Windows 2000™ and certificates generated by other PKI systems may not be accepted by Windows 2000™.
Therefore, what is needed is a method and computer program in which a user having a PKI system may generate certificates that can be used for another PKI system in a single simple process that does not require the reentry of data. Further, this method and computer program should allow for user authentication and user mobility from one computer to another.